Wild River Lamprey Welfare: Ancient Fish in Modern Rivers

River lampreys are ancient jawless fish that spend their larval stage in river sediment before migrating to sea, and face welfare challenges from barriers, water quality, and climate change.

Key Facts

River lampreys are among the most ancient vertebrates, with a body plan unchanged for 360 million years
Larvae (ammocoetes) spend 3-7 years buried in silt, filter-feeding on organic material
Adult lampreys migrate to sea to parasitise fish before returning to rivers to spawn and die
Migratory barriers including weirs and sluices prevent upstream migration to spawning sites
River lamprey populations have declined significantly across Europe due to barriers, water quality, and siltation
The species is protected under the Habitats Directive; it is illegal to damage lamprey habitats
Lamprey passes have been installed at some weirs to facilitate migration
The welfare implications of barrier blockage include failed reproduction after years of larval development

Welfare Considerations

River lamprey welfare involves a lifecycle where years of larval development culminate in a migration and spawning event that barriers can entirely prevent. An adult lamprey blocked from reaching its spawning grounds by a weir that lacks an adequate fish pass fails to complete a reproductive journey that is the culmination of 3-7 years of growth. This is a welfare harm with a clear structural cause and an achievable solution - fish pass installation. River restoration that removes unnecessary barriers and installs effective passes at remaining structures directly improves the welfare prospects of individual lampreys attempting to complete their reproductive migration.

What You Can Do

Support river barrier removal and fish pass installation campaigns
Donate to river restoration organisations working on lamprey migration restoration
Report lamprey spawning activity to wildlife record centres to assist with distribution monitoring
Advocate for fish pass design standards that specifically accommodate lamprey migration requirements
Support water quality improvement that reduces siltation and maintains larval habitat quality